Tap And Die Questions

[bosephus]

hmm , not being a standard size had not crossed my mind . i do have a very small bit of wiggle room size wise
the closest standard size tap i can find would be a metric M22x1 @ 26 threads per inch and for all intents and purposes is close enough to what i had drawn to call it good .

and as to why not single point the threads and get exactly what i want ,.. two reasons . the first being i do not think my little g0602 is ridged enough to hang a threading tool
that far out and achieve the perfect threads i am looking for here . i know my little lathe pretty well now after over a year of steady use , i can foresee a lot of chatter marks
and those i do not want .
the second is ,.. it is a smallish deep hole to thread , and it will be a one shot deal , i screw up and im out quite a bit of money in materials .
spending the money on a good quality tap is just a form of cheap insurance .
and if everything works to plan i will have a continued future use for it

 

[rallycat]

Try 7/8"-20 - that is a standard NEF (national extra fine) size. Nominal size is .025" over your design which you ought to have room for.

 

[rick9345]

hi guys and gals

i have a project coming up that i need to buy a tap and die for , i normally would just single point the threads
but in this case due to extremely high material costs ( many hundreds of dollars ) i feel that it would be better safe then sorry and invest in a high quality hss tap and die to take as much risk out of the equation as possible .

so what i need to do is tap a hole .850X20 tp 2.450 inches deep to a shoulder and the corresponding threads on the mating piece .

so my questions are ,.... tapping to the shoulder ,.. do i need to start with a taper tap and then switch to a bottom tap , or can i just use a bottom tap from start to finish .

and what brands to look at and who to buy them from , this is most definitely a case of wanting quality versus a price point

Start design over to classic/common tools available to be compatible with available experience. Painting ones self into a corner is never a good experience.
Heed above suggestions.

 

[Bill C.]

Best to start with a tapered tap, then go to a bottoming especially for that depth. Can't say I have a preference for what brand, as long as it is HSS.

If you are using a milling machine or drill press look into buying a spring loaded center used in conjunction with a
Tap-handle to keep the tap straight when starting. That is a odd thread size to me.

Be sure to keep the chips cleaned out as you are taping. I know it can be a pain having to backout the tap after a couple of turns to remove chips

 

[David VanNorman]

You need to go with as close to standard as you can get. You are also cutting a male thread so it makes sense to use as close to standard as possible. Find something close and go with it.